Digestive System Flashcards
Intracellular digestion
Occurs within the cell, often membrane bound vesicles
Extracellular digestion
Occurs outside of the cell, within lumen/tract
Outline the pathway of food starting from oral cavity.
Oral cavity –> Pharynx –> Esophagus –> Stomach –> Small intestine –> Large intestine – Anus
What type of digestion occurs in the mouth?
-Mechanical (mastication) and chemical (salivary amylase)
Salivary amylase
-Breaks starch into maltose (disacc)
Peristalsis
- Rhythmic waves of involuntary muscular contractions
- Esophagus
What separate the stomach and esophagus?
-Lower esophageal (cardiac) sphincter
Compare the relative pressure of the thoracic and abdominal cavities
- Thoracic cavity (where body of esophagus is) negatively pressured relative to environment on inhalation
- Abdominal cavity (+) pressure
Gastroesphageal reflux disease (GERD)
- Results from pressure gradients
- Reflux of gastric material into esophagus
What are chief cells?
- In gastric glands
- Produce pepsinogen
What are parietal cells?
- In gastric glands
- Synthesize/release HCl and intrinsic factor (absorb vitamin B12)
What is the role of HCl?
- Converts pepsinogen to pepsin
- Kills bacteria
What kind of digestion is in stomach?
-Mechanical (churning) and Chemical
Where does chyme pass into?
-Duodenum through pyloric sphincter
What lines the stomach walls?
-Gastric mucosa secreted by mucous cells
Where does chemical digestion finish?
-Small intestine
What are the sections of the small intestine?
-Duodenum, Jejunum, Ileum
What do villi consist of?
-Capillaries and lacteals
Where do large fatty acids and glycerol go from the small intestine?
-Pass to lacteals then moved to liver where they’re converted to tryglycerides
Which nutrients are actively absorbed?
-Amino acids and glucose
Where does most digestion in small intestines occur?
-Duodenum
What does intestinal mucosa secrete?
- Lipases
- Aminopeptidases
- Disaccharidases
Where and what is the function of gastrin?
- Produced by G cells in duodenum
- Stimulate histamine and pepsinogen secretion
- Stimulate parietal cells
Where and what is the function of intrinsic?
- Secreted by parietal cells
- Facilitate absorption of vitamin B12
Cholecystokinin (CCK)
- Produced by I cells of duodenal/jejunal mucosa
- Stimulate panreatic snzyme and somatostatin secretion
- Stimulate gallbladder contraction
- Hunger suppressant
Secretin
- Synthesized by S cells of upper intestine
- Stimulate secretion of bicarbonate-containing substances from pancreas
- Inhibit gastric emptying and gastric acid production
Bile
- Produced by liver and stored in gallbladder
- Release to small intestine to emulsify fats
What is the purpose of emulsifying fats?
-Increase surface area for lipases
What are functions of the liver?
- Store glycogen
- Convert ammonia to urea
- Protein synthesis
- Detoxification
- Cholesterol metabolism
What does the pancreas produce?
- Amylase, trypsin, lipase
- Secrete bicarbonate containing substances
Large intestine
-Absorb salt and any water not absorbed by small intestine
Rectum
-Transient storage of feces –> anus
